The invention relates to electrostatic shutter tubes, and particularly to improvements in so-called "light-shutter" image tubes for use in high speed photography wherein substantially orthogonal pairs of deflection plates provide for deflection of an electron image to any of different locations, in two directions or dimensions, on a phosphor screen. The plates are positioned so that the tube length is not increased over tubes having only one pair of deflection plates, and the deflection sensitivity is maximized for both pairs of plates.
U.S. Pat. No. 2,946,895 issued to R. G. Stoudenheimer et al. on July 26, 1960, discloses an image tube of the "light-shutter" type having a single pair of electrostatic deflection plates for directing a focused electron-image to any of different locations, in one dimension, on a phosphor screen. The deflection plates are located in a field-free region within the anode of the tube where they can be closely spaced to provide maximum deflection sensitivity without adversely affecting the focusing field between the apex of the anode and the photocathode. A drawback of the disclosed deflection structure is that the electron image can only be directed in one dimension on the screen.
U.S. Pat. No. 2,859,377 issued to J. E. Clemens et al. on Nov. 4, 1958, discloses an electronic high speed shutter in which two pairs of orthogonally disposed deflection plates are located at the same longitudinal distance from an electron image producing cathode. Since both pairs of plates lie in the same transverse plane, the spacing between the oppositely disposed pairs cannot be as close as the above-described single pair of plates in the Stoudenheimer et al. structure and, therefore, the deflection sensitivity of the Clemens et al. structure is less than that of the Stoudenheimer et al. structure. Additionally, since the pairs of deflection plates are unshielded by an anode, the deflection fields can adversely affect the electrical focusing field. Additional deflection structures showing two pairs of deflection plates located in a transverse plane and spaced an equal longitudinal distance from a cathode are disclosed in U.S. Pat. No. 3,761,614 and in U.S. Pat. No. 3,973,117 issued to D. J. Bradley on Sept. 25, 1973 and on Aug. 3, 1976, respectively. In the Bradley patents, the pairs of deflection plates are located between the anode and the screen so that the deflection fields cannot adversely affect the focusing field; however, the location of the two pairs of plates prevent the close spacing achieved by the single pair of plates in the Stoudenheimer et al. patent and, thus, the deflection sensitivity of the Bradley structures is less than that achieved by the Stoudenheimer structure.
U.S. Pat. No. 4,224,511 issued to Brjuknevich et al. on Sept. 23, 1980, discloses an image intensifier tube having two pairs of deflection plates located at increasing longitudinal distances from an image producing cathode. While such a structure permits a close transverse spacing between the pairs of deflection plates, it increases the length of the tube, thereby increasing the electron image transit time from the cathode to the screen, thus, decreasing the speed of the tube.